hmm... well, the Allies and Chinese Tanks/Armored Vehicles are harder to hijack, so it's better to just order them, the lower factions, like the VZ, UP, and PLAV, are easier, but lighter in terms of firepower and armor, also, you need to press the appropriate buttons, and fast enough, to hijack a vehicle (again, Allies/Chinese you need to tap FAST)Keyboard:

By the way... there should be an update to auto-jack whenever the animation for hijacking has gone off, that way you can hijack at the fastest possible speed, and all of the hijacking require the same buttons to be pushed, and I've done this countless times, the Puma Light Tank will always have B and A (Melee and Jump) keyed for the jackings, so I'm gonna guess all the others will too.

Yeah they do, if iv not had my normal bath of coffee i tend to jump on and see what comes up before i actualy take the tank/heli, that way ill know what to do in future lol, the amount of times iv been kicked out a littlebird PMSL